Snort mailing list archives

Re: DNS traffic or portscan?


From: spyguy703 <spyguy703 () yahoo com>
Date: Tue, 26 Feb 2002 11:26:56 -0800

I will try that. Some individuals have told me that snort is only seeing one 
side of regular DNS traffic and thus is showing up as a portscan.

possible? if so, what did i do wrong with snort?


On Tuesday 26 February 2002 11:24 am, Glenn Forbes Fleming Larratt wrote:
It's not a sure thing, but, examining from stimulus-response perspective,
it's mighty convenient that the source port numbers increment more or less
sequentially - across, supposedly, two different source hosts. It's a
reasonable possibility someone spoofed the addresses of win32host,
snorthost, or both.

Configuring Snort to log traffic to dns1.mydomain.com might help determine
(a) source MAC addresses, to confirm or deny the spoofing theory,
(b) contents of the DNS requests stimulating this response (DDNS? Cache
poisoning? version.bind queries? etc.).

      -g

On Tue, 26 Feb 2002, spyguy703 wrote:
Can someone please help me figure out what to make of this traffic that I
pulled from portscan.log?

I had DNS admins checkout the DNS server and they are certain that it has
not been compromised and that no one is scanning me.

"dns1.mydomain.com" is our DNS server on the internet
"win32host" is a windows host on the DMZ network (publicly routable IP)
"snorthost" is the management interface on the snort host that monitors
this network.


Feb 22 13:20:20 dns1.mydomain.com:53 -> win32host:1092 UDP
Feb 22 13:20:21 dns1.mydomain.com:53 -> win32host:1096 UDP
Feb 22 13:20:21 dns1.mydomain.com:53 -> win32host:1099 UDP
Feb 22 13:20:21 dns1.mydomain.com:53 -> win32host:1101 UDP
Feb 22 13:20:22 dns1.mydomain.com:53 -> win32host:1103 UDP
Feb 22 13:20:24 dns1.mydomain.com:53 -> win32host:1105 UDP
Feb 22 14:10:47 dns1.mydomain.com:53 -> snorthost:1108 UDP
Feb 22 14:10:47 dns1.mydomain.com:53 -> snorthost:1109 UDP
Feb 22 14:10:48 dns1.mydomain.com:53 -> snorthost:1110 UDP
Feb 22 14:10:49 dns1.mydomain.com:53 -> snorthost:1111 UDP
Feb 22 14:10:49 dns1.mydomain.com:53 -> snorthost:1112 UDP
Feb 22 14:10:53 dns1.mydomain.com:53 -> snorthost:1113 UDP
Feb 22 14:10:53 dns1.mydomain.com:53 -> snorthost:1114 UDP
Feb 22 14:47:08 dns1.mydomain.com:53 -> snorthost:1122 UDP
Feb 22 14:47:08 dns1.mydomain.com:53 -> snorthost:1123 UDP
Feb 22 14:47:08 dns1.mydomain.com:53 -> snorthost:1124 UDP
Feb 22 14:47:10 dns1.mydomain.com:53 -> snorthost:1125 UDP
Feb 22 14:47:10 dns1.mydomain.com:53 -> snorthost:1126 UDP
Feb 22 14:47:14 dns1.mydomain.com:53 -> snorthost:1127 UDP
Feb 22 14:47:14 dns1.mydomain.com:53 -> snorthost:1128 UDP
Feb 22 17:38:45 dns1.mydomain.com:53 -> snorthost:1132 UDP
Feb 22 17:38:45 dns1.mydomain.com:53 -> snorthost:1133 UDP
Feb 22 17:38:45 dns1.mydomain.com:53 -> snorthost:1134 UDP
Feb 22 17:38:47 dns1.mydomain.com:53 -> snorthost:1135 UDP
Feb 22 17:38:47 dns1.mydomain.com:53 -> snorthost:1136 UDP
Feb 22 17:38:53 dns1.mydomain.com:53 -> snorthost:1137 UDP
Feb 22 17:38:53 dns1.mydomain.com:53 -> snorthost:1138 UDP

                              Glenn Forbes Fleming Larratt
                              Rice University Network Management
                              glratt () rice edu



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